In general, a gas laser oscillator has a pair of electrodes disposed in a hermetically-sealed enclosure, and a laser gas sealed in the enclosure is forcefully circulated by a blower. The laser gas is excited by electric discharge caused by the pair of electrodes. After having been caused to resonate between a partial reflection mirror and a total reflection mirror, the thus-excited laser is radiated outside. The radiated laser is fed to a machining head through a plurality of mirrors, to thereby machine a workpiece on a machining table.
Such a blower that circulates the laser gas in the laser oscillator is handled as a kind of expendable article. When the blower stops for some reason during laser oscillation, circulation of a gas laser is interrupted, which impairs optical components or electrodes in the enclosure. Further, when the laser oscillator is used for laser machining, the stoppage of the blower results in impairment of optical components and electrodes in the laser oscillator, so that machining is continued while the quality of the laser beam remains anomalous. Thus, machining failures arise over a wide area, thereby inducing great influence. In general maintenance of a related-art blower, deterioration of a blower is determined from the estimated life of the blower predicted from operating time of the laser oscillator through periodic checks.
A method for determining an anomaly in a blower is described in JP-A-1-106487 wherein there is detected an anomaly from a relationship between an electric current of a blower coasting after stoppage of a laser oscillator and a coasting time; and a method is described in JP-A-2003-110172 for detecting an anomaly by comparing an electric current output, from an inverter section which supplies power to a blower, with a predetermined value.
Drawbacks of the related-art determination of deterioration of a blower, which is performed by estimating the life of the blower, include enforced early replacement of a blower in view of preventing maintenance and the inability to detect deterioration without periodic checks. The related-art method for detecting an anomaly described in JP-A-1-106487 can detect an anomaly only during a period of stoppage of the blower, and encounters difficulty in preventing occurrence of anomalous stoppage of the blower during the operation of the oscillator or the machine. In contrast, the related-art for detecting an anomaly in a blower described in JP-A-2003-110172 enables to prevent anomalous stoppage of a blower during machining operation. However, a current value of the blower is usually changed by the pressure of a laser gas in an enclosure as well as by deterioration of the blower. Hence, the method has a drawback of determining changes in the pressure of a laser gas as deterioration of the blower.